That's because you buy shitty headphones. My Stax SR-3 headphones are 50 years old.
Despite thorough personal grooming and only having them at a studio desk, the part of the cable that wraps around the top of the ear will still get eaten through to the copper by the oil on my ears after about two years.
Shitty or not, headphones—at least the ones that see thorough use—are consumables.
How much should I expect to pay for quality headphones with the jack that last?